With the advent of model-based controls for gas turbines, and an increasing emphasis on improving turbine performance and heat recovery steam generator (“HRSG”) life and performance, it has become desirable to have a better understanding of the distribution of exhaust temperatures in gas turbines.
Currently, the existing instrumentation in gas turbine stations typically measures the exhaust temperature of a turbine at multiple positions circumferentially, but only at one position radially, in the turbine exhaust.
During the performance testing of gas turbines, it is common practice to place, at multiple circumferential positions around the exhaust frame of the turbine, exhaust temperature rakes that measure exhaust temperature at a number of radial positions in the turbine exhaust. These rakes measure a more complete distribution of the gas turbine's exhaust temperature, and can be used to define a correction to the gas turbine station's instrumentation measurement. However, these rakes are typically not robust enough to be used as long term, production instrumentation. The design of production rakes faces the challenge of being mechanically robust in a high temperature/flow environment, with concerns of dynamic responses. In addition, any such design must have a negligible impact on turbine performance.